Fingerprint recognition integrated circuit and fingerprint recognition device including the same

ABSTRACT

A fingerprint recognition device includes a display, a touch sensor panel (TSP) which senses a touch, and a fingerprint recognition integrated circuit (FPIC) which scans a fingerprint. The FPIC includes a pixel including a photoelectric element which receives light reflected by the fingerprint, a low noise amplifier (LNA) which outputs a signal voltage by converting an electric charge received from the photoelectric element, and an analog-to-digital converter (ADC) which converts the signal voltage into a digital signal. The ADC includes a variable reference voltage generator which provides a variable reference voltage, a comparator which adds the variable reference voltage to the signal voltage, performs correlated double sampling on the result of the addition, and outputs a comparison signal by comparing the result of the correlated double sampling with a ramp voltage, and a counter which outputs the digital signal by counting the comparison signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2019-0001564, filed on Jan. 7, 2019 in the KoreanIntellectual Property Office, the disclosure of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

Exemplary embodiments of the present inventive concept relate to afingerprint recognition integrated circuit (FPIC) and a fingerprintrecognition device including the same.

DISCUSSION OF THE RELATED ART

As fingerprint recognition devices are used more frequently in mobiledevices, rapid technological developments are being made. A fingerprintrecognition device, that is, a fingerprint sensor, was typicallyinitially applied to a physical home button in mobile devices. However,with the recent tendency to minimize outer bezels, which may result inthe need to remove the physical home button, methods of applying afingerprint sensor to a display are being researched.

The methods of applying a fingerprint sensor to a display largelyinclude capacitive, optical, and ultrasonic methods. The capacitivemethod has a poor sensing distance characteristic, and thus, problemsmay arise when using the capacitive method on a display. The ultrasonicmethod has drawbacks of high sensor cost and large computing power. Theoptical method is vulnerable to dry or low-temperature environments, buthas advantages over other methods in terms of sensing distance and cost.

SUMMARY

Exemplary embodiments provide a fingerprint recognition device withreduced internal complexity and high resolution.

Exemplary embodiments also provide a fingerprint recognition integratedcircuit (FPIC) with reduced internal complexity and high resolution.

According to an exemplary embodiment of the present inventive concept, afingerprint recognition device includes a display which outputs animage, a touch sensor panel (TSP) which senses a touch on the display,and a fingerprint recognition integrated circuit (FPIC) which scans afingerprint touched on the display. The FPIC includes a pixel includinga photoelectric element for receiving light reflected by thefingerprint, a low noise amplifier (LNA) which outputs a signal voltageby converting an electric charge received from the photoelectricelement, and an analog-to-digital converter (ADC) which converts thesignal voltage into a digital signal. The ADC includes a variablereference voltage generator which provides a variable reference voltage,a comparator which adds the variable reference voltage to the signalvoltage, performs correlated double sampling on the result of theaddition, and outputs a comparison signal by comparing the result of thecorrelated double sampling with a ramp voltage, and a counter whichoutputs the digital signal by counting the comparison signal.

According to an exemplary embodiment of the present inventive concept, afingerprint recognition device includes a display which outputs animage, a TSP which senses a touch on the display and generates touchcoordinates, a display drive integrated circuit (DDI) which illuminatesa scan area of the display determined based on the touch coordinates, anFPIC which generates fingerprint image data by scanning a fingerprint inthe scan area, and a processor which receives the fingerprint imagedata.

According to an exemplary embodiment of the present inventive concept,an FPIC includes a sensor which includes a pixel array including aphotoelectric element which receives light reflected by a fingerprint,and a read-out integrated circuit (IC) which processes an output of thesensor. The read-out IC includes a plurality of analog front ends (AFEs)connected to each of output lines respectively corresponding to columnsof the pixel array. At least one of the AFEs includes a low noiseamplifier (LNA) which outputs a signal voltage by converting an electriccharge received through an output line, a low pass filter (LPF) whichremoves high-frequency noise of the signal voltage, and ananalog-to-digital converter (ADC) which converts the signal voltage intoa digital signal. The ADC includes a variable reference voltagegenerator which provides a variable reference voltage, a comparatorwhich adds the variable reference voltage to the signal voltage,performs correlated double sampling on the result of the addition, andoutputs a comparison signal by comparing the result of the correlateddouble sampling with a ramp voltage, and a counter which outputs thedigital signal by counting the comparison signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present inventive concept willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a fingerprint recognition device accordingto exemplary embodiments.

FIG. 2 is a flowchart illustrating the operation of the fingerprintrecognition device of FIG. 1.

FIG. 3 is a flowchart illustrating the operation of a fingerprintrecognition device according to exemplary embodiments.

FIG. 4 is a flowchart illustrating the initial setting of a fingerprintrecognition device according to exemplary embodiments.

FIG. 5 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

FIG. 6 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

FIG. 7 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

FIG. 8 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

FIG. 9 is a flowchart illustrating a fingerprint recognition process ofa fingerprint recognition device according to exemplary embodiments.

FIG. 10 is a detailed flowchart illustrating the processes ofidentifying whether there is an intention to perform fingerprintrecognition and determining a scan area, as described with reference toFIG. 9.

FIG. 11 is a conceptual diagram for describing the process ofdetermining the scan area, as described with reference to FIG. 10.

FIG. 12 is a detailed flowchart illustrating a process in which afingerprint recognition device identifies whether there is an intentionto perform fingerprint recognition and determines a scan area accordingto exemplary embodiments.

FIG. 13 is a conceptual diagram for describing determining the scanarea, as described with reference to FIG. 12.

FIG. 14 is a block diagram of a fingerprint recognition integratedcircuit (FPIC) according to exemplary embodiments.

FIG. 15 is a detailed block diagram of a sensor of FIG. 14.

FIG. 16 is a detailed block diagram of a first read-out IC of FIG. 14.

FIG. 17 is a detailed block diagram of an analog front end (AFE) of FIG.16.

FIG. 18 is a block diagram of an FPIC according to exemplaryembodiments.

FIG. 19 is a block diagram of an FPIC according to exemplaryembodiments.

FIG. 20 is a block diagram of an FPIC according to exemplaryembodiments.

FIG. 21 is an equivalent circuit diagram of an FPIC according toexemplary embodiments.

FIG. 22 is a timing diagram of operation signals of FIG. 21.

FIG. 23 is a conceptual diagram for describing a fingerprint recognitionoperation of a fingerprint recognition device according to exemplaryembodiments.

FIG. 24 is a graph illustrating a ramp voltage and a counting operationof a fingerprint recognition device according to exemplary embodiments.

FIG. 25 is a voltage graph illustrating a signal voltage of afingerprint recognition device according to exemplary embodiments.

FIG. 26 is a graph illustrating an input dynamic range (IDR) of thefingerprint recognition device according to the embodiments;

FIG. 27 illustrates the structure of a pixel array of a sensor of anFPIC according to exemplary embodiments.

FIG. 28 is a timing diagram for describing a scan operation of the FPICaccording to exemplary embodiments.

FIG. 29 is a timing diagram for describing a scan operation of an FPICaccording to exemplary embodiments.

FIG. 30 is a conceptual block diagram of an FPIC according to exemplaryembodiments.

FIG. 31 is a conceptual block diagram of an FPIC according to exemplaryembodiments.

DETAILED DESCRIPTION

Exemplary embodiments of the present inventive concept will be describedmore fully hereinafter with reference to the accompanying drawings. Likereference numerals may refer to like elements throughout theaccompanying drawings.

It will be understood that the terms “first,” “second,” “third,” etc.are used herein to distinguish one element from another, and theelements are not limited by these terms. Thus, a “first” element in anexemplary embodiment may be described as a “second” element in anotherexemplary embodiment.

A fingerprint recognition device according to exemplary embodiments willnow be described with reference to FIG. 1.

FIG. 1 is a block diagram of a fingerprint recognition device accordingto exemplary embodiments.

Referring to FIG. 1, the fingerprint recognition device according toexemplary embodiments includes a display 11, a fingerprint recognitionintegrated circuit (FPIC) 10, a touch sensor panel (TSP) 12, a displaydrive integrated circuit (IC) (DDI) 13, and a processor 14 (e.g., anapplication processor AP).

The display 11 may output image data. The display 11 may be located onthe front of the fingerprint recognition device so that a user can seevisual information provided on the display 11. The display 11 may becontrolled by the DDI 13.

The FPIC 10 may be coupled to the display 11, and may recognize afingerprint touched on the display 11. For example, the FPIC 10 mayrecognize a fingerprint input provided on the display 11. The FPIC 10may cover the whole display 11. For example, in exemplary embodiments,the FPIC 10 is not located in only a specific portion of the display 11,but rather, covers an entirety of the display 11. Thus, the FPIC 10 canscan fingerprint inputs provided on all parts of the display 11.

The FPIC 10 may be synchronized with the DDI 13. Thus, a clock CLKprovided to the FPIC 10 and a clock CLK provided to the DDI 13 may besynchronized with each other.

In addition, the FPIC 10 may transmit image data Di to the processor 14as a result of fingerprint recognition. The image data Di may be imagedata of a fingerprint recognized by the FPIC 10. For example, the FPIC10 may scan a fingerprint to obtain image data Di corresponding to thefingerprint, and may transmit the image data Di to the processor 14.

The TSP 12 may be coupled to the display 11 and may sense a touch. Forexample, when the display 11 is touched, the TSP 12 may sense the touchand transmit coordinate data of the touch to the processor 14. Since theTSP 12 is coupled to the display 11 and detects a touch applied to afront surface of the display 11, the display 11 and the TSP 12 mayfunction as an input/output device of the fingerprint recognitiondevice. The FPIC 10 may be a fingerprint image input device.

The DDI 13 may drive the output of the display 11. An image of the lightand color of the display 11 may be output by the DDI 13. The imageoutput by the DDI 13 may be controlled by the processor 14. That is, theDDI 13 may be controlled by the processor 14.

The processor 14 may control the TSP 12, the DDI 13, and the FPIC 10.The processor 14 may receive a touch sensed by the TSP 12 and afingerprint sensed by the FPIC 10. The processor 14 may control theoutput of the DDI 13 based on the received inputs. In addition, theprocessor 14 may be responsible for the management of the TSP 12, theDDI 13, and the FPIC 10.

FIG. 2 is a flowchart illustrating the operation of the fingerprintrecognition device of FIG. 1.

Referring to FIG. 2, at operation S100, the TSP 12 senses a touch andtransmits coordinate data to the processor 14.

The coordinate data may be, for example, a plurality of coordinate datasensed by the TSP 12. For example, when a user continuously providestouch inputs, the TSP 12 may continuously transmit the coordinate datato the processor 14 in real time. For example, when multiple touchinputs are provided, the TSP 12 may continuously transmit differentcoordinate data corresponding to the multiple touch inputs to theprocessor 14 in real time as the multiple touch inputs are provided.

At operation S200, the processor 14 identifies whether there is anintention to perform fingerprint recognition.

For example, the processor 14 may identify whether a user intends tohave his or her fingerprint recognized. That is, when it is detectedthat a touch input may have been provided, the processor 14 maydetermine whether there is an intention that fingerprint identificationbe performed. The processor 14 may determine whether there is theintention to perform fingerprint recognition based on the coordinatedata received from the TSP 12.

If it is determined that there is the intention to perform fingerprintrecognition, the fingerprint recognition device may continuously performfingerprint recognition. However, if it is determined there is not anintention to perform fingerprint recognition, the fingerprintrecognition device should not perform fingerprint recognition. Forexample, performing fingerprint recognition when it is not intended mayresult in decreased performance and efficiency of the fingerprintrecognition device. Therefore, identifying whether there is theintention to perform fingerprint recognition may improve the performanceand efficiency of the fingerprint recognition device.

For example, according to exemplary embodiments, when a user's fingertouches the display 11 without an intention to perform fingerprintrecognition, and the TSP 12 recognizes the touch, fingerprintrecognition is not performed, as described in further detail below.

At operation S300, if it was previously determined that there was anintention to perform fingerprint recognition, the processor 14determines a scan area.

The scan area may refer to a part of the display 11 that is less thanthe entirety of the display 11. For example, to perform fingerprintrecognition in the entire area of the display 11, it may be required toincrease the size of the FPIC 10 and to significantly increase thecomplexity of the configuration of the FPIC 10. To address theseproblems, the fingerprint recognition device according to exemplaryembodiments may determine (or set) a part of the display 11 as the scanarea and perform fingerprint recognition only within the scan area.

To this end, the scan area may be determined around the coordinate data.That is, the scan area may be defined with reference to the coordinatedata. Determining the scan area will be described in more detail below.

At operation S400, the processor 14 transmits a command to illuminatethe scan area to the DDI 13.

For example, as described above, a part of the display 11 (and not theentirety of the display 11) may be set as the scan area in whichfingerprint recognition is to be performed. Accordingly, in thefingerprint recognition device according to exemplary embodiments, onlythe scan area in which a fingerprint is scanned is illuminated, andother parts of the display 11 that do not correspond to the scan areaare not driven during fingerprint recognition. Thus, fingerprintrecognition can be performed efficiently.

At operation S500, the DDI 13 illuminates the scan area.

For example, the DDI 13 may output white light or cyan light to the scanarea of the display 11. This light may be output, reflected by afingerprint, and used to perform fingerprint recognition on thefingerprint.

At operation S600, the processor 14 transmits a command (e.g., a scancommand) to the FPIC 10 causing the scan area to be scanned. Atoperation S700, the fingerprint recognition device scans the scan area.

For example, in exemplary embodiments, the FPIC 10 may obtain image dataof a fingerprint by scanning only the scan area of the display 11 andnot scanning the entire area of the display 11. Here, although the scanarea is only a part of the display 11, any part of the display 11 can beconfigured as the scan area. That is, different parts of the display 11may be selected as the scan area. Therefore, the FPIC 10 can performfingerprint recognition for the entire area of the display 11.

The FPIC 10 may detect light output by the DDI 13 and then reflected bya fingerprint. In exemplary embodiments, the illuminating and scanningof the scan area are performed almost simultaneously within a very shorttime.

However, since the display 11 is composed of a plurality of pixels andthe DDI 13 controls the output of light for each of the pixels, a delayin the order of milliseconds may occur from a first pixel to a lastpixel. In exemplary embodiments, the scan operation of the FPIC 10 takesthis delay into consideration, and the FPIC 10 and the DDI 13 mayreceive clocks synchronized with each other and may synchronize theirrespective operations.

At operation S800, the FPIC 10 transmits fingerprint image data to theprocessor 14.

For example, referring to FIG. 1, the FPIC 10 may obtain the image dataDi and transmit the image data Di to the processor 14. The processor 14may receive the image data Di and perform authentication or otheroperations based on the image data Di.

In exemplary embodiments, the processor 14 may perform fingerprintrecognition. Alternatively, in exemplary embodiments, the TSP 12, theDDI 13 and the FPIC 10 may perform fingerprint recognition instead ofthe processor 14.

FIG. 3 is a flowchart illustrating the operation of a fingerprintrecognition device according to exemplary embodiments. For convenienceof explanation, a further description of elements and technical aspectspreviously described may be omitted.

At operation S1100, a TSP 12 identifies whether there is an intention toperform fingerprint recognition.

For example, referring to FIG. 1, the TSP 12 may identify whether thereis the intention to perform fingerprint recognition based on coordinatedata of a touch input by a user. If there is the intention to performfingerprint recognition, the fingerprint recognition device maycontinuously perform fingerprint recognition. If there is no intentionto perform fingerprint recognition, the fingerprint recognition devicedoes not perform fingerprint recognition.

Referring again to FIG. 3, at operation S1200, if it is determined thatthere is the intention to perform fingerprint recognition, the TSP 12determines a scan area.

For example, referring to FIG. 1, in exemplary embodiments, the TSP 12may determine the scan area without involvement of the processor 14.Accordingly, since communication between the processor 14 and the TSP 12is not needed in exemplary embodiments to determine the scan area, ascan operation can be performed more concisely and rapidly.

Referring again to FIG. 3, at operation S1300, the TSP 12 transmits thecoordinate data to the DDI 13 and the FPIC 10.

Then, at operation S1400, the DDI 13 illuminates the scan area.

For example, referring to FIG. 1, in exemplary embodiments, the DDI 13may illuminate the scan area without involvement of the processor 14.

Referring again to FIG. 3, at operation S1500, the FPIC 10 scans thescan area.

For example, referring to FIG. 1, in exemplary embodiments, the FPIC 10may scan the scan area without involvement of the processor 14. Thescanning may be performed by detecting light that is reflected afterbeing output by the DDI 13.

Referring again to FIG. 3, at operation S1600, the FPIC 10 transmitsfingerprint image data to the processor 14.

In exemplary embodiments, the DDI 13, the TSP 12 and the FPIC 10 canperform fingerprint recognition with little or no involvement of theprocessor 14. This reduces the amount of computation needed to beperformed by the processor 14 and eliminates unnecessary communicationwith the processor 14, thereby increasing the speed of the fingerprintrecognition operation.

FIG. 4 is a flowchart illustrating the initial setting of a fingerprintrecognition device according to exemplary embodiments.

Referring to FIG. 4, the fingerprint recognition device according toexemplary embodiments may register a fingerprint and a pattern throughan initial setting.

First, at operation S2100, a fingerprint is registered.

For example, referring to FIG. 1, a fingerprint of a user's finger isregistered and stored as basic data for fingerprint recognition. Thatis, in exemplary embodiments, authentication and other subsequentoperations can only be performed when the same fingerprint as theregistered fingerprint is recognized.

In exemplary embodiments, a fingerprint can be registered only throughthe FPIC 10, the registered fingerprint may be managed by the processor14, and the fingerprint registration may be performed through theoperation of the processor 14, the FPIC 10, the DDI 13 and/or the TSP12.

Referring again to FIG. 4, next, at operation 52200, a patternindicating an intention to perform fingerprint recognition isregistered.

The pattern may later be used to identify whether there is the intentionto perform fingerprint recognition. The pattern may be, for example, aspecific gesture, the number of fingers that touch the display 11, atouch at a specific position, or the distance between fingers that touchthe display 11. However, the pattern is not limited thereto. Forexample, in exemplary embodiments, even though it may be detected that afinger has touched the display 11, fingerprint recognition is onlyperformed if the pattern registered in operation 52200 is detectedfirst.

FIG. 5 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

Referring to FIG. 5, the pattern indicating the intention to performfingerprint recognition may be a specific shape drawn on a display 11and a TSP 12 with a finger F. For example, a gesture such drawing a Z, 0or W without taking the finger F off the display 11 may be registered asthe pattern indicating the intention to perform fingerprint recognition.

That is, when a gesture registered in advance with the finger F is inputto the display 11 and the TSP 12, it can be determined that there is theintention to perform fingerprint recognition. For example, in exemplaryembodiments, assuming that a gesture of drawing a Z without taking thefinger F off the display 11 is registered as the pattern, fingerprintrecognition will only be performed upon detection of the gesture ofdrawing a Z.

FIG. 6 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

Referring to FIG. 6, the pattern indicating the intention to performfingerprint recognition may correspond to the number of fingers F thattouch the display 11 at the same time. For example, when three fingers Fsimultaneously touch the display 11, it may be determined that there isthe intention to perform fingerprint recognition. In exemplaryembodiments, the pattern may correspond to less than three fingers F ormore than three fingers F.

FIG. 7 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

Referring to FIG. 7, the pattern indicating the intention to performfingerprint recognition may correspond to a specific area of the display11 and the TSP 12 being touched by a finger F. For example, in exemplaryembodiments, a specific area may be set as a target detection area, andonly when the finger F touches the target detection area of the display11 and the TSP 12 is it determined that there is the intention toperform fingerprint recognition.

FIG. 8 is a conceptual diagram for describing how a pattern is used by afingerprint recognition device to identify an intention to performfingerprint recognition according to exemplary embodiments.

Referring to FIG. 8, the pattern indicating the intention to performfingerprint recognition may be the distance between two fingers F thattouch a display 11. For example, if the distance between two fingers Fthat touch the display 11 is registered as a first distance D1,subsequently, when two fingers F that touch the display 11 are spacedapart by the first distance D1, it may be determined that there is theintention to perform fingerprint recognition.

In exemplary embodiments, it may be determined that there is theintention to perform fingerprint recognition as long as the distancebetween the two fingers F is at least the registered distance D1. Forexample, in exemplary embodiments, there is no limit on how much largerthan D1 the distance between the two fingers F is. That is, once thedistance between the two fingers F reaches the registered distance D1,it is determined that there is the intention to perform fingerprintrecognition.

Alternatively, in exemplary embodiments, a maximum threshold larger thanD1 may also be registered. In such exemplary embodiments, if thedistance between the two fingers F is greater than D1 but is alsogreater than the maximum threshold, it is determined that there is nointention to perform fingerprint recognition. That is, in such exemplaryembodiments, it is determined that there is an intention to performfingerprint recognition when the distance between the two fingers F isat least equal to D1 and is less than or equal to the maximum threshold.

FIG. 9 is a flowchart illustrating a fingerprint recognition process ofa fingerprint recognition device according to exemplary embodiments.

Referring to FIG. 9, at operation S3100, the fingerprint recognitiondevice may be woken up in response to a touch sensed. For example, thefingerprint recognition device may be in a sleep state or a low-powerstate, in which the fingerprint recognition device consumes less power,until the fingerprint recognition device is woken up in response to atouch sensed.

For example, referring to FIG. 1, the TSP 12 may sense a touch and wakeup the fingerprint recognition device.

Referring again to FIG. 9, at operation S3200, it is identified whetherthere is an intention to perform fingerprint recognition.

If a user does not intend to have his or her fingerprint recognized(absence), a guide message is output at operation S3300.

Referring to FIG. 1, the guide message may be output to the display 11.If the user intends to have his or her fingerprint recognized, the guidemessage may be a message requesting the user to input a preregisteredpattern. Through this message, the user's intention can be identifiedmore clearly.

Referring again to FIG. 9, at operation S3400, it is identified againwhether there is the intention to perform fingerprint recognition.

Since the user can input, once again, the pattern indicating theintention to perform fingerprint recognition in response to the guidemessage, the fingerprint recognition device can identify the user'sintention once again.

If there is no intention to perform fingerprint recognition (absence),the woken-up fingerprint recognition device switches back to the mode itwas in before being woken up. For example, the fingerprint recognitiondevice may switch back to a power-off mode or low-power mode.

Here, the power-off mode or low-power mode refers to a mode in which nopower or minimum power is provided to prevent unnecessary batteryconsumption.

If it is determined in operation S3200 or S3400 that there is theintention to perform fingerprint recognition (presence), a scan area isdetermined at operation S3600.

For example, referring to FIG. 1, the determination of the scan area maybe performed by the processor 14 or the TSP 12. The scan area is an areain which a fingerprint is scanned. The scan area may be a part of thedisplay 11.

Referring again to FIG. 9, at operation S3700, the scan area may beilluminated.

For example, referring to FIG. 1, the scan area may be illuminated bythe DDI 13. Here, the processor 14 may command the DDI 13 to illuminatethe scan area, or the DDI 13 may illuminate the scan area without beingprompted by the processor 14.

Referring again to FIG. 9, fingerprint image data is transmitted atoperation S3800.

For example, referring to FIG. 1, the image data may be obtained by theFPIC 10. The FPIC 10 may generate the image data Di by detecting lightthat is emitted by the DDI 13 and then reflected by a fingerprint.

The FPIC 10 may transmit the obtained image data of the fingerprint tothe processor 14.

FIG. 10 is a detailed flowchart illustrating the processes ofidentifying whether there is the intention to perform fingerprintrecognition and determining the scan area, as described with referenceto FIG. 9. FIG. 11 is a conceptual diagram for describing the process ofdetermining the scan area, as described with reference to FIG. 10.

Referring to FIG. 10, identifying whether there is the intention toperform fingerprint recognition (operation S3200 in FIG. 9) includes thefollowing operations.

First, at operation S3210, a pattern is recognized/detected.

The pattern may be a pattern registered in advance to identify theintention to perform fingerprint recognition as described above, forexample, with reference to FIGS. 5 through 8.

Next, at operation S3220, the recognized pattern is compared with theregistered pattern.

If the registered pattern is different from the recognized pattern, itis determined that there is no intention to perform fingerprintrecognition (absence). If the registered pattern is the same as therecognized pattern, it is determined that there is the intention toperform fingerprint recognition (presence).

If it is determined that the registered pattern is different from therecognized pattern at operation S3220, a guide message is output atoperation S3300. After the guide message is outputted, it is identifiedagain whether there is the intention to perform fingerprint recognitionat operation S3400. If it is determined that there is not the intentionto perform fingerprint recognition, a power-off mode or low-power modeis entered into at operation S3500, as described above.

If it is determined at operations S3220 and S3400 that there is theintention to perform fingerprint recognition, a reference time isinitiated and observed at operation S3610.

Here, the reference time is a time in units of microseconds ormilliseconds, and may be a time given until coordinates for a scan areaare determined. That is, when it is determined that there is theintention to perform fingerprint recognition based on a pattern inputusing a finger F, the reference time may be measured from the time ofdetermination. For example, the reference time may be measured from thetime that it is determined that there exists the intention to performfingerprint recognition.

Next, at operation S3620, center coordinates are detected.

For example, referring to FIG. 11, the center coordinates may refer tocoordinates of a central part of the scan area. For example, the centercoordinates may refer to coordinates of a point that the finger Ftouches after the reference time elapses.

Referring again to FIG. 10, at operation S3630, the scan area isdetermined based on the center coordinates.

For example, referring to FIG. 1, the scan area may be an area of aspecific size defined around the center coordinates. The scan area maybe determined by the processor 14, the TSP 12, or the FPIC 10.

Accordingly, after inputting a pattern to the display 11 and the TSP 12,a user can naturally perform fingerprint recognition in an area in whichthe finger F is located.

FIG. 12 is a detailed flowchart illustrating a process in which afingerprint recognition device identifies whether there is an intentionto perform fingerprint recognition and determines a scan area accordingto exemplary embodiments. FIG. 13 is a conceptual diagram for describingdetermining the scan area, as described with reference to FIG. 12.

Recognizing a pattern (operation S3210), comparing a registered patternwith the recognized pattern (operation S3220), outputting a guidemessage (operation S3300), identifying again whether there is theintention to perform fingerprint recognition (operation S3400), andentering a power-off mode or a low-power mode (operation S3500) are thesame as the corresponding operations of FIG. 10. Accordingly, forconvenience of explanation, a further description thereof is omitted.

If it is determined in operations S3220 and S3400 that there is theintention to perform fingerprint recognition, an end of a current touchand a next touch are sensed at operation S3611.

For example, referring to FIGS. 1 and 13, a touch for inputting apattern and then another touch made after a finger F is taken off thedisplay 11 may be sensed. The touch sensing may be performed by the TSP12.

Referring again to FIG. 12, center coordinates are detected at operationS3620.

For example, referring to FIG. 13, the center coordinates may refer tocoordinates of a point that the finger F touches after being taken offthe display 11. A scan area is determined based on the centercoordinates at operation S3630, which is the same as that of FIG. 10,and thus will not be described again.

Therefore, after inputting a pattern to the display 11 and the TSP 12, auser can designate the scan area by making a touch for fingerprintrecognition. This method can more clearly separate the patternrecognition and the fingerprint recognition processes, thus preventingthe confusion of the user. For example, in exemplary embodiments, apattern may be input at a first location of the display 11, and the scanarea may be designated as a second location of the display 11 differentfrom the first location.

Hereinafter, FPICs according to exemplary embodiments will be describedwith reference to FIGS. 14 through 28. The FPICs to be described withreference to FIGS. 14 through 28 have the same configuration as the FPIC10 of FIG. 1. Thus, a further description of elements and technicalaspects previously described may be omitted.

FIG. 14 is a block diagram of an FPIC 10 according to exemplaryembodiments.

Referring to FIG. 14, the FPIC 10 according to exemplary embodimentsincludes a sensor 100 and a first read-out integrated circuit (IC) 200.

The sensor 100 may receive light reflected by a fingerprint and convertthe received light into an electric charge. The sensor 100 may transmitthe electric charge to the first read-out IC 200. The first read-out IC200 may read the output of the sensor 100 and output image data Di ofthe fingerprint.

FIG. 15 is a detailed block diagram of the sensor 100 of FIG. 14.

Referring to FIG. 15, the sensor 100 may include a controller 110 and afirst pixel array 120.

The controller 110 may control the first pixel array 120. The controller110 may control the reset, selection and amplification operations ofpixels Pix constituting the first pixel array 120, and control thedriving of each transfer transistor TX.

The controller 110 may independently control a plurality of rows R0through Rn of the first pixel array 120.

The first pixel array 120 may include a plurality of pixels Pix (P(0,0)through P(n,m)). Herein, n and m are positive integers. The pixels Pixmay be arranged in the rows R0 through Rn and a plurality of columnsrespectively including a plurality of output lines C0 through Cm. Thatis, the pixels Pix arranged in each column may share one of the outputlines C0 through Cm.

Each of the pixels Pix may include a photodiode PD and a transfertransistor TX.

The photodiode PD may be a photoelectric element that receives light andgenerates an electric charge. The photodiode PD may generate an electriccharge corresponding to light reflected by a fingerprint.

The transfer transistor TX may transfer the electric charge generated bythe photodiode PD to the first read-out IC 200 through one of the outputlines C0 through Cm. That is, when a gate voltage is applied to thetransfer transistor TX, an output of a pixel Pix corresponding to thetransfer transistor TX may be output to a corresponding one of theoutput lines C0 through Cm.

FIG. 16 is a detailed block diagram of the first read-out IC 200 of FIG.14.

Referring to FIG. 16, the first read-out IC 200 includes a plurality ofanalog front ends (AFEs) 210_0 through 210_m. Each AFE may also bereferred to as an AFE circuit.

The AFEs 210_0 through 210_m may correspond to the output lines C0through Cm, respectively. That is, an equal number of the AFEs 210_0through 210_m to the number of columns of the first pixel array 120 maybe connected in a one-to-one correspondence to the columns of the firstpixel array 120.

Respective outputs of the AFEs 210_0 through 210_m may form image dataDi of a fingerprint, and the image data Di may be output.

FIG. 17 is a detailed block diagram of an AFE of FIG. 16.

Referring to FIG. 17, a first AFE 210_0 may include a low noiseamplifier (LNA) 211, a low pass filter (LPF) 212, and ananalog-to-digital converter (ADC) 213. Although the structure of onlythe first AFE 210_0 is illustrated for the sake of convenience, thestructures of the AFEs 210_1 through 210_m may be the same as thestructure of the first AFE 210_0.

The LNA 211 may be connected to any one of the output lines C0 throughCm. The LNA 211 may convert an electric charge output from a pixel intoa voltage.

The LPF 212 may remove high-frequency noise of the voltage output fromthe LNA 211.

The ADC 213 may output image data of the pixel by converting the analogvoltage output from the LPF 212 into a digital signal.

FIG. 18 is a block diagram of an FPIC according to exemplaryembodiments. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIG. 18, the FPIC according to exemplary embodimentsincludes a second read-out IC 201.

The second read-out IC 201 may include a plurality of AFEs 210_0 through210_j and a first multiplexer 230. Herein, j is a positive integer.

The first multiplexer 230 may connect a plurality of output lines C0through Cm to the AFEs 210_0 through 210_j. The first multiplexer 230may connect the (m+1) output lines C0 through Cm to the (j+1) AFEs 210_0through 210_j. Here, m may be a number greater than j.

The first multiplexer 230 may reduce the complexity of the FPIC byreducing the number of AFEs. In addition, although signals of the outputlines C0 through Cm are not processed at the same time, they can all beeventually processed by the AFEs 210_0 through 210_j. Therefore, thereis no signal loss, or signal loss may be reduced. Accordingly, the FPICaccording to exemplary embodiments provides improved performance.

FIG. 19 is a block diagram of an FPIC according to exemplaryembodiments. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIG. 19, the FPIC according to exemplary embodimentsincludes a third read-out IC 202.

The third read-out IC 202 may include a plurality of LNAs 211_0 through211_m, a plurality of LPFs 212_0 through 212_m, a second multiplexer240, and a plurality of ADCs 213_0 through 213_k. Herein, k is apositive integer.

The LNAs 211_0 through 211_m and the LPFs 212_0 through 212_m maycorrespond one-to-one to a plurality of output lines C0 through Cm. Thatis, the number of the LNAs 211_0 through 211_m and the number of theLPFs 212_0 through 212_m may be (m+1), which is equal to the number ofthe output lines C0 through Cm.

The second multiplexer 240 may connect the LPFs 212_0 through 212_m tothe ADCs 213_0 through 213_k. The second multiplexer 240 may connect the(m+1) LNAs 211_0 through 211_m and the (m+1) LPFs 212_0 through 212_m tothe (k+1) ADCs 213_0 through 213_k. Here, m may be a number greater thank.

The second multiplexer 240 may reduce the complexity of the FPICaccording to exemplary embodiments by reducing the number of ADCs. Inaddition, although signals of the LPFs 212_0 through 212_m are notprocessed at the same time, they can all be eventually processed by theADCs 213_0 through 213_k. Therefore, there is no signal loss, or signalloss may be reduced.

FIG. 20 is a block diagram of an FPIC according to exemplaryembodiments. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIG. 20, the FPIC according to exemplary embodimentsincludes a fourth read-out IC 203.

The fourth read-out IC 203 may include a first multiplexer 230, aplurality of LNAs 211_0 through 211_j, a plurality of LPFs 212_0 through212_j, a second multiplexer 240, and a plurality of ADCs 213_0 through213_p. Herein, p is a positive integer.

The first multiplexer 230 may connect a plurality of output lines C0through Cm to the LNAs 211_0 through 211_j. The first multiplexer 230may connect the (m+1) output lines C0 through Cm to the (j+1) LNAs 211_0through 211_j. Here, m may be a number greater than j.

The LNAs 211_0 through 211_j and the LPFs 212_0 through 212_j maycorrespond one-to-one to each other. Here, the number of the LNAs 211_0through 211_j and the number of the LPFs 212_0 through 212_j may be(j+1) which is smaller than (m+1), that is, is the number of the outputlines C0 through Cm.

The second multiplexer 240 may connect the LPFs 212_0 through 212_j tothe ADCs 213_0 through 213_p. The second multiplexer 240 may connect the(j+1) LNAs 211_0 through 211_j and the (j+1) LPFs 212_0 through 212_j tothe (p+1) ADCs 213_0 through 213_p. Here, j may be a number greater thanp.

FIG. 21 is an equivalent circuit diagram of an FPIC according toexemplary embodiments. FIG. 22 is a timing diagram of operation signalsof FIG. 21. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIGS. 21 and 22, a sensor 100 includes a plurality ofpixels Pix. Each of the pixels Pix includes a photodiode PD and atransfer transistor. In FIG. 21, three transfer transistors, that is, afirst transfer transistor TX_R0, a second transfer transistor TX_R1, anda third transfer transistor TX_R2 are illustrated. However, exemplaryembodiments are not limited to this case, and the number of transfertransistors can vary.

An LNA 211 may include a first amplifier A1, a charge capacitor Cf, anda first switch SW1.

A first reference voltage VREF1 may be applied to a positive (+)terminal of the first amplifier A1. A negative (−) terminal of the firstamplifier A1 may be connected to an output line of a pixel Pix. Thecharge capacitor Cf may be connected to the negative terminal of thefirst amplifier A1 and a first output voltage terminal Vo1. The firstswitch SW1 may be connected in parallel to the charge capacitor Cf.

When the first switch SW1 is operated by a reset signal RSTn, the chargecapacitor Cf may be initialized according to the reset signal RSTn. Whenthe reset signal RSTn is turned off while a gate voltage of the firsttransfer transistor TX_R0 is turned on, the charge capacitor Cf may becharged with an electric charge Q accumulated in the photodiode PD.

Here, the first output voltage Vo1 may be Vo1=VREF1+Q/Cf.

An LPF 212 may include a resistor R, a second switch SW2, and a firstcapacitor C1. The second switch SW2 may operate according to an LPFsignal LPF. To speed up settling, the LPF signal LPF may turn on thesecond switch SW2 and then turn off the second switch SW2. Accordingly,a second output voltage Vo2 may quickly transition from a transientresponse to a saturation response.

An ADC 213 may include a third switch SW3, a variable reference voltagegenerator 214, a fourth switch SW4, a second amplifier A2, a secondcapacitor C2, a third capacitor C3, a fifth switch SW5, a sixth switchSW6, and a counter 215. The counter 215 may also be referred to as acounter circuit.

The third switch SW3 and the fourth switch SW4 may be operated by aswitch signal SW. The third switch SW3 and the fourth switch SW4 mayoperate in a complementary manner. That is, when any one of the thirdswitch SW3 and the fourth switch SW4 is turned on, the other may beturned off.

The switch signal SW may be turned off and then turned on. Accordingly,the third switch SW3 may be opened, and the fourth switch SW4 may beclosed. Then, as the fourth switch SW4 is opened, the third switch SW3may be closed.

Therefore, when the third switch SW3 is opened while the fourth switchSW4 is closed, the first capacitor C1 of the LPF 212 may be charged withthe first output voltage Vo1, and the second output voltage Vo2 may be avariable reference voltage Vrefa. Then, when the third switch SW3 isclosed while the fourth switch SW4 is opened, the second output voltageVo2 may become Vo2=Vrefa−Vo1.

The fifth switch SW5 and the sixth switch SW6 may be driven by an ADCreset signal RSTadc. The ADC reset signal RSTadc may be turned on forinitialization and then turned off. Accordingly, a positive terminal ofthe second amplifier A2 may be initialized to a second reference voltageVREF2, and a negative terminal and an output terminal of the secondamplifier A2 may also be initialized to the second reference voltageVREF2.

The second capacitor C2, the third capacitor C3 and the second amplifierA2 may constitute a comparator which compares a ramp voltage RAMP and athird output voltage Vi3 n. That is, 0 may be output when the thirdoutput voltage Vi3 n is smaller than the ramp voltage RAMP, and 1 may beoutput when the third output voltage Vi3 n is greater than the rampvoltage RAMP.

The sensor 100 outputs a reset output and then a signal output. Here,the reset output refers to an output when there is no signal, and thesignal output refers to the reset output containing a signal component.

Accordingly, the ramp voltage RAMP in a first section P1 may be used tocount the reset output, and the ramp voltage RAMP in a second section P2may be used to count the signal output. In FIG. 22, CNT may denotecounting. The final image data Di may be generated after the secondsection P2.

Later, the ADC 213 performs correlated double sampling for removingnoise by subtracting the reset output from the signal output. To thisend, the ADC 213 may use the first capacitor C1 of the LPF 212. Aconventional ADC uses two to four capacitors for correlated doublesampling. In contrast, the ADC 213 of the FPIC according to exemplaryembodiments uses only one capacitor, thereby reducing the complexity ofthe circuit.

The variable reference voltage generator 214 may generate the variablereference voltage Vrefa. The variable reference voltage Vrefa may begenerated to adjust an input dynamic range (IDR) of the ADC 213.

For example, the third output voltage Vi3 n is a value obtained bysubtracting the second output voltage Vo2 from the second referencevoltage VREF2. That is, Vi3 n=VREF2−Vo2. Since Vo2=Vrefa−Vo1 andVo1=VREF1+Q/Cf, Vi3 n=VREF2−Vrefa+VREF1+Q/Cf.

The third output voltage Vi3 n may be adjusted by the first referencevoltage VREF1, the second reference voltage VREF2, and the variablereference voltage Vrefa.

The counter 215 may convert an analog signal into a digital signal bycounting an output of the second amplifier A2, that is, an output of thecomparator. The digital signal may be the image data Di.

FIG. 23 is a conceptual diagram for describing a fingerprint recognitionoperation of a fingerprint recognition device according to exemplaryembodiments.

Referring to FIG. 23, a fingerprint of a finger F may include ridges Rand valleys V. The ridges R may be convex portions adjacent to thesurface of a display 11, and the valleys V may be concave portionsspaced apart from the surface of the display 11. The difference betweenlight reflected by the ridges R and light reflected by the valleys V maybe very small.

FIG. 24 is a graph illustrating the ramp voltage RAMP and a countingoperation of a fingerprint recognition device according to exemplaryembodiments.

Referring to FIGS. 21, 22 and 24, a counter 215 may perform countingusing a count pulse Pulse_Count. When the ramp voltage RAMP has a firstslope S1, the counter 215 may generate a digital signal of a first bit“a1 bit” during a first count time t_Count 1. Alternatively, when theramp voltage RAMP has a second slope S2 smaller than the first slope 51,the counter 215 may generate a digital signal of a second bit “a2 bit”during a second count time t_Count 2.

That is, in a single slope ADC having a single slope, the smaller theslope, the higher the resolution. However, reducing the slope toincrease the resolution may increase the time for counting to the secondcount time t_Count 2 which is greater than the first count time t_Count1.

FIG. 25 is a voltage graph illustrating a signal voltage of afingerprint recognition device according to exemplary embodiments. FIG.26 is a graph illustrating an IDR of the fingerprint recognition deviceaccording to exemplary embodiments.

Referring to FIGS. 23 through 25, an FPIC according to exemplaryembodiments may have high resolution because the difference betweenvalleys V and ridges R is very small. Assuming that an output of theFPIC is a full signal voltage Vsig, the full signal voltage Vsig mayhave several sections of values from a minimum voltage Vmin to a maximumvoltage Vmax in order for high resolution.

However, since a band that actually varies according to the differencebetween the valleys V and the ridges R is very small, this can beconsidered separately. For example, the full signal voltage Vsig can beconsidered as the sum of an offset and a partial signal voltage Vsig′.In this case, it is not necessary to use the entire second count timet_Count 2 by making a portion where the ramp voltage RAMP is actuallymeasured and converted have the second slope S2. Instead, only the firstcount time t_Count 1 can be used for the second slope S2.

For example, referring to FIG. 26, since the third output voltage Vi3 nis defined as Vi3 n=VREF2−Vrefa+VREF1+Q/Cf by the above-describedequation, it can be adjusted to the IDR of the ramp voltage Vramp havingthe second slope S2 by adjusting the variable reference voltage Vrefa.Accordingly, a count time t_Count can be as short as the first counttime t_Count 1 of FIG. 24.

As described above, in exemplary embodiments, the third output voltageVi3 n can be adjusted by adjusting the variable reference voltage Vrefawhile the first reference voltage VREF1 and second reference voltageVREF2 are fixed. However, in an FPIC according to exemplary embodiments,not only the variable reference voltage Vrefa but also the firstreference voltage VREF1 and/or the second reference voltage VREF2 can bevaried to adjust the third output voltage Vi3 n to the IDR of the rampvoltage Vramp.

An FPIC according to exemplary embodiments will now be described withreference to FIGS. 27 and 28. For convenience of explanation, a furtherdescription of elements and technical aspects previously described maybe omitted.

FIG. 27 illustrates the structure of a pixel array of a sensor of anFPIC according to exemplary embodiments. FIG. 28 is a timing diagram fordescribing a scan operation of the FPIC according to exemplaryembodiments.

Referring to FIG. 27, a first pixel array 120 includes a plurality ofpixels P(0,0) through P(n,m). The first pixel array 120 includes aplurality of rows H1 through Hn, and the rows H1 through Hn include afirst row H1, a second row H2 . . . through an n^(th) row Hn.

Referring to FIGS. 27 and 28, the FPIC according to exemplaryembodiments may perform a dummy capture operation for fingerprintrecognition and then perform a main capture operation. Here, the dummycapture operation refers to scanning a scan area without an exposureintegration time (EIT).

The EIT refers to a period of time during which each pixel receivesexternal light. The EIT may last from one scan to a next scan.

Therefore, a meaningless scan, that is, the dummy capture operation, maybe performed in order to initialize the EIT, and then the main captureoperation may be performed after a first pause N1 for making respectiveEITs of the pixels equal.

In the dummy capture operation or the main capture operation, capturingor scanning may be performed on a row-by-row basis, and the time takento capture each of the rows H1 through Hn may be the same row scan time1H.

In addition, an EIT may be given to each row. A first EIT EIT1 of thefirst row H1 may last from a time when the dummy capture operation ofthe first row H1 ends to a time when the main capture operation of thefirst row H1 begins. A second EIT EIT2 of the second row H2 may lastfrom a time when the dummy capture operation of the second row H2 endsto a time when the main capture operation of the second row H2 begins.

Similarly, an n^(th) EIT EITn of the n^(th) row Hn may last from a timewhen the dummy capture operation of the n^(th) row Hn ends to a timewhen the main capture operation of the n^(th) row Hn begins.

The first pause N1 may be a period of time generated by these EITs.

FIG. 29 is a timing diagram for describing a scan operation of an FPICaccording to exemplary embodiments. For convenience of explanation, afurther description of elements and technical aspects previouslydescribed may be omitted.

Referring to FIGS. 21, 22, 27 and 29, the FPIC according to exemplaryembodiments may perform a sub capture operation between the dummycapture operation and the main capture operation.

Since the dummy capture operation is performed for initialization, thereis no EIT at all. However, the sub capture operation has an EIT, andthus, a second pause N2 may exist between the dummy capture operationand the sub capture operation.

In addition, since an EIT for the main capture operation is alsoutilized, a first pause N1 may exist between the sub capture operationand the main capture operation.

Since an EIT is given to each row, a (1_1)^(th) EIT EIT1_1 of a firstrow H1 may last from a time when the dummy capture operation of thefirst row H1 ends to a time when the sub capture operation of the firstrow H1 begins, and a (2_1)^(th) EIT EIT2_1 of the first row H1 may lastfrom a time when the sub capture operation of the first row H1 ends to atime when the main capture operation of the first row H1 begins. The(2_1)^(th) EIT EIT2_1 may be longer than the (1_1)^(th) EIT EIT1_1.

A (1_2)^(th) EIT EIT1_2 of a second row H2 may last from a time when thedummy capture operation of the second row H2 ends to a time when the subcapture operation of the second row H2 begins, and a (2_2)^(th) EITEIT2_2 of the second row H2 may last from a time when the sub captureoperation of the second row H2 ends to a time when the main captureoperation of the second row H2 begins. The (2_2)^(th) EIT EIT2_2 may belonger than the (1_2)^(th) EIT EIT1_2.

Similarly, a (1_n)^(th) EIT EIT1_n of an n^(th) row Hn may last from atime when the dummy capture operation of the n^(th) row Hn ends to atime when the sub capture operation of the n^(th) row Hn begins, and a(2_n)^(th) EIT EIT2_n of the n^(th) row Hn may last from a time when thesub capture operation of the n^(th) row Hn ends to a time when the maincapture operation of the n^(th) row Hn begins. The (2_n)^(th) EIT EIT2_nmay be longer than the (1_n)^(th) EIT EIT1_n. Referring to FIGS. 21 and22, a reset output and a signal output are used for correlated doublesampling performed to remove noise. However, in exemplary embodiments,the reset output may remove only the noise of the LNA 211, the LPF 212and the ADC 213, but not the noise of the sensor 100.

Therefore, to remove the noise of the sensor 100, the FPIC according toexemplary embodiments may perform the sub capture operation in whichtransfer transistors of the sensor 100 are turned on and then the resultof the sub capture operation is subtracted from the result of the maincapture operation.

However, if the sub capture operation has a long EIT, more signalcomponents may be included in the sub capture operation. Therefore, theEIT (EIT1_1, EIT1_2, . . . , EIT1_n) of the sub capture operation may bemade very short, so that there is substantially no signal component inthe sub capture operation. Accordingly, the second pause N2 may be veryshort as compared with the first pause N1.

Since the FPIC according to exemplary embodiments can completely removeeven the noise of the sensor 100 through the sub capture operation, theFPIC can perform more accurate and reliable fingerprint recognition.

FIG. 30 is a conceptual block diagram of an FPIC according to exemplaryembodiments. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIG. 30, the FPIC according to exemplary embodiments mayinclude a first pixel array 120, a plurality of AFEs 210_0 through210_m, and a plurality of subtractors 220_0 through 220_(m−1).

The first pixel array 120 may include a plurality of pixels P(0,0)through P(n,m), and the AFEs 210_0 through 210_m may be connected in aone-to-one correspondence to a plurality of output lines C0 through Cmcorresponding to columns of the first pixel array 120.

Each of the subtractors 220_0 through 220_(m−1) may output a differencebetween outputs of two adjacent ones of the AFEs 210_0 through 210_m.That is, each of the subtractors 220_0 through 220_(m−1) may output adifference signal obtained by subtracting an output of one AFE from anoutput of another AFE. Thus, each of the subtractors 220_0 through220_(m−1) may output a difference between the digital signals Di of twoadjacent AFEs. Since the subtractors 220_0 through 220_(m−1) subtractoutputs of the (m+1) AFEs 210_0 through 210_m from each other, msubtractors 220_0 through 220_(m−1) may be utilized. Each of thesubtractors 220_0 through 220_(m−1) may also be referred to as asubtractor circuit.

Since the difference signals are signals from which a noise componentcommon to all pixels has been removed, the difference signals mayinclude clearer more highly reliable fingerprint image data.

Therefore, the FPIC according to exemplary embodiments can perform moreaccurate fingerprint recognition.

FIG. 31 is a conceptual block diagram of an FPIC according to exemplaryembodiments. For convenience of explanation, a further description ofelements and technical aspects previously described may be omitted.

Referring to FIG. 31, the FPIC according to exemplary embodiments mayinclude a second pixel array 121, a plurality of AFEs 210_0 through210_(m+1), and a plurality of subtractors 220_0 through 220_m.

The second pixel array 121 may include a plurality of pixels P(0,0)through P(n,m+1). Of the pixels P(0,0) through P(n,m+1), one columnP(0,m+1) through P(n,m+1) may be a column for outputting noise and maybe connected to a noise output line C_noise. Although the columnconnected to the noise output line C_noise is a last column in FIG. 31,exemplary embodiments are not limited to this case.

Of the AFEs 210_0 through 210_(m+1), AFEs excluding an AFE connected tothe noise output line C_noise may all be connected to the subtractors220_0 through 220_m. Since the AFE connected to the noise output lineC_noise among the AFEs 210_0 through 210_(m+1) outputs only noise, thesubtractors 220_0 through 220_m may subtract the noise from outputs ofthe AFEs not connected to the noise output line C_noise among the AFEs210_0 through 210_(m+1).

Accordingly, the noise common to all pixels may be removed from theoutputs. When the second pixel array 121 has (m+2) columns, the numberof the subtractors 220_0 through 220_m may be (m+1), which is smallerthan (m+2) by one.

Since output signals of the subtractors 220_0 through 220_m are signalsfrom which a noise component common to all pixels has been removed, theoutput signals may include clearer and more highly reliable fingerprintimage data.

Therefore, exemplary embodiments provide an FPIC capable of performingmore accurate fingerprint recognition.

As is traditional in the field of the inventive concept, exemplaryembodiments are described, and illustrated in the drawings, in terms offunctional blocks, units and/or modules. Those skilled in the art willappreciate that these blocks, units and/or modules are physicallyimplemented by electronic (or optical) circuits such as logic circuits,discrete components, microprocessors, hard-wired circuits, memoryelements, wiring connections, etc., which may be formed usingsemiconductor-based fabrication techniques or other manufacturingtechnologies. In the case of the blocks, units and/or modules beingimplemented by microprocessors or similar, they may be programmed usingsoftware (e.g., microcode) to perform various functions discussed hereinand may optionally be driven by firmware and/or software. Alternatively,each block, unit and/or module may be implemented by dedicated hardware,or as a combination of dedicated hardware to perform some functions anda processor (e.g., one or more programmed microprocessors and associatedcircuitry) to perform other functions.

While the present inventive concept has been particularly shown anddescribed with reference to the exemplary embodiments thereof, it willbe understood by those of ordinary skill in the art that various changesin form and detail may be made therein without departing from the spiritand scope of the present inventive concept as defined by the followingclaims.

What is claimed is:
 1. A fingerprint recognition device, comprising: adisplay which outputs an image; a touch sensor panel (TSP) which sensesa touch on the display; and a fingerprint recognition integrated circuit(FPIC) which scans a fingerprint touched on the display, wherein theFPIC comprises: a pixel comprising a photoelectric element whichreceives light reflected by the fingerprint; a low noise amplifier (LNA)which outputs a signal voltage by converting an electric charge receivedfrom the photoelectric element; and an analog-to-digital converter (ADC)which converts the signal voltage into a digital signal, wherein the ADCcomprises: a variable reference voltage generator which provides avariable reference voltage; a comparator which adds the variablereference voltage to the signal voltage, performs correlated doublesampling on the result of the addition, and outputs a comparison signalby comparing the result of the correlated double sampling with a rampvoltage; and a counter which outputs the digital signal by counting thecomparison signal.
 2. The fingerprint recognition device of claim 1,wherein the FPIC comprises a pixel array in which a plurality of pixels,including the pixel, is arranged in rows and columns, wherein the FPICinitializes outputs of the pixels by performing a dummy captureoperation, and subsequently scans the fingerprint by performing a maincapture operation.
 3. The fingerprint recognition device of claim 2,wherein a first pause exists after the dummy capture operation andbefore the main capture operation.
 4. The fingerprint recognition deviceof claim 3, wherein the FPIC performs a sub capture operation betweenthe dummy capture operation and the main capture operation.
 5. Thefingerprint recognition device of claim 3, wherein a second pause islocated after the dummy capture operation and before the sub captureoperation, the first pause is located after the sub capture operationand before the main capture operation, and the second pause is shorterthan the first pause.
 6. The fingerprint recognition device of claim 1,wherein the FPIC comprises a pixel array in which a plurality of pixels,including the pixel, is arranged in rows and columns, wherein the pixelarray comprises a plurality of output lines, each output line is sharedby pixels in the same column, the LNA is one of a plurality of LNAs, andeach of the LNAs is connected to any one of the output lines.
 7. Thefingerprint recognition device of claim 6, wherein a number of theoutput lines is greater than a number of the LNAs, and the FPIC furthercomprises a multiplexer which connects the output lines to the LNAs. 8.The fingerprint recognition device of claim 6, wherein the FPIC furthercomprises a low pass filter (LPF) which removes high-frequency noise ofthe signal voltage, and the signal voltage from which the high-frequencynoise has been removed is transmitted to the ADC.
 9. The fingerprintrecognition device of claim 8, wherein the LPF is one of a plurality ofLPFs, the ADC is one of a plurality of ADCs, each of the ADCs isconnected to any one of the LPFs, a number of the LPFs is greater than anumber of the ADCs, and the FPIC further comprises a multiplexer whichconnects the LPFs to the ADCs.
 10. The fingerprint recognition device ofclaim 6, wherein the ADC is one of a plurality of ADCs, and the FPICfurther comprises: a plurality of analog front ends (AFEs) connected toeach of the output lines, wherein each of the AFEs comprises one of theLNAs and one of the ADCs and outputs the digital signal; and asubtractor which outputs a difference between the digital signals of twoadjacent AFEs.
 11. The fingerprint recognition device of claim 6,wherein the ADC is one of a plurality of ADCs, and the pixel arraycomprises a noise output column which does not receive a signal andoutputs only noise, and wherein the FPIC further comprises a pluralityof analog front ends (AFEs) connected to each of the output lines, eachAFE comprising one of the LNAs and one of the ADCs and outputting thedigital signal, and a subtractor which subtracts the digital signal ofan AFE corresponding to the noise output column from the digital signalsof the other AFEs.
 12. A fingerprint recognition device, comprising: adisplay which outputs an image; a touch sensor panel (TSP) which sensesa touch on the display and generates first touch coordinates; a displaydrive integrated circuit (DDI) which illuminates a scan area of thedisplay determined based on the first touch coordinates; a fingerprintrecognition integrated circuit (FPIC) which generates fingerprint imagedata by scanning a fingerprint in the scan area; and a processor whichreceives the fingerprint image data.
 13. The fingerprint recognitiondevice of claim 12, wherein the scan area is determined when it isidentified that there is an intention to perform fingerprintrecognition.
 14. The fingerprint recognition device of claim 13, whereinthe processor identifies whether there is the intention to performfingerprint recognition and determines the scan area when there is theintention to perform fingerprint recognition.
 15. The fingerprintrecognition device of claim 13, wherein the TSP identifies whether thereis the intention to perform fingerprint recognition and determines thescan area when there is the intention to perform fingerprintrecognition.
 16. The fingerprint recognition device of claim 13, whereinidentifying whether there is the intention to perform fingerprintrecognition comprises determining whether a preregistered pattern and acurrently recognized pattern are the same.
 17. The fingerprintrecognition device of claim 13, wherein identifying whether there is theintention to perform fingerprint recognition comprises outputting aguide message when there is no intention to perform fingerprintrecognition, and subsequently identifying again whether there is theintention to perform fingerprint recognition.
 18. The fingerprintrecognition device of claim 13, wherein, when it is identified thatthere is the intention to perform fingerprint recognition, the scan areais determined using second touch coordinates of a touch made after areference time measured from the time of identification.
 19. Thefingerprint recognition device of claim 12, wherein the DDI and the FPICrespectively receive first and second clocks, and the first and secondclocks are synchronized with each other.
 20. A fingerprint recognitionintegrated circuit (FPIC), comprising: a sensor which comprises a pixelarray comprising a photoelectric element which receives light reflectedby a fingerprint; and a read-out integrated circuit (IC) which processesan output of the sensor, wherein the read-out IC comprises a pluralityof analog front ends (AFEs) connected to each of output linesrespectively corresponding to columns of the pixel array, wherein atleast one of the AFEs comprises: a low noise amplifier (LNA) whichoutputs a signal voltage by converting an electric charge receivedthrough an output line; a low pass filter (LPF) which removeshigh-frequency noise of the signal voltage; and an analog-to-digitalconverter (ADC) which converts the signal voltage into a digital signal,wherein the ADC comprises: a variable reference voltage generator whichprovides a variable reference voltage; a comparator which adds thevariable reference voltage to the signal voltage, performs correlateddouble sampling on the result of the addition, and outputs a comparisonsignal by comparing the result of the correlated double sampling with aramp voltage; and a counter which outputs the digital signal by countingthe comparison signal.